Hanetz and shekia (sunrise and sunset times) are influenced by elevation.
This page allows you to display sunrise and sunset times for
a specific elevation profile.
Caution: Entering the wrong information will produce incorrect zmanim;
if there's something you don't know, please leave it blank.

Horizon elevations
For Elevation of east horizon enter the elevation of the point on the eastern horizon where the sun will rise.
For Elevation of west horizon enter the elevation of the point on the western horizon where the sun will set.

If you do not specify any Horizon Elevation we will assume it is the same as Your Elevation. Whenever Horizon Elevation and Your Elevation are equal, the impact it has on sunrise/sunset times is minimal.

If the Horizon elevation is greater than Your elevation the zmanim will be calculated
as if the Horizon elevation was the same as Your elevation.

(שבת קיח: ”יהא חלקי ממכניסי שבת בטבריא“)

If your view of the horizon is blocked by obstructions (such as nearby hills or mountains) determine the point
where the sun will set behind the obstructions and use the elevation of that point as your Horizon elevation.

(מהרי"ל הל' תפילה ”מכל מקום אחורי ההרים עוד היום גדול“')

How do I find my elevation?
Among others, a convenient tool for checking elevations is Google Earth
(earth.google.com).
Set units of measurement
to meters (under Tools > Options) and then hover over a location to display
its elevation at the bottom of the window.
Measuring your elevation with a GPS (or mobile app such as "GPS Test") is
also fine provided that the GPS accurately converts elevation above
ellipsoid to elevation above sea level. (Note: MyZmanim cannot take
responsibility for the accuracy of elevation data provided by Google Earth or
your GPS.)